Membrane-assisted fluid separation apparatus and method

ABSTRACT

This present invention relates to a fluid separation module adapted to separate a given fluid mixture into permeate and retentate portions using bundles of hollow fiber membranes. The membranes may be composed of different kinds of membranes depending on the application being used to separate the fluid mixture. The fluid separation module may be used to separate fluid mixtures by a number of different processes, including but not limited to, pervaporation, vapour permeation, membrane distillation (both vacuum membrane distillation and direct contact membrane distillation), ultra filtration, microfiltration, nanofiltration, reverse osmosis, membrane stripping and gas separation. The present invention also provides an internal heat recovery process applied in association with those fluid separation applications where separation takes place by evaporation through the membrane of a large portion of the feed into permeate. Desalination and contaminated water purification by means of vacuum membrane distillation are just two examples where the internal heat recovery process may be applied. In these two examples, large portions of the feed are separated by membranes into a high purity water permeate stream by evaporation through the membranes and into a retentate stream containing a higher concentration of dissolved components than present in the feed. In this process the permeate vapour that is extracted from the fluid separation module is compressed by an external compressor to increase the temperature of the vapour higher than the temperature of the feed entering the separation module. Heat from the permeate vapour at the elevated temperature is transferred back to the incoming feed fluid mixture entering the fluid separation module in a condenser/heat exchange.

FIELD OF THE INVENTION

[0001] This invention relates to fluid separation. In particular, thisinvention relates to a fluid separation apparatus comprising of hollowfiber membranes used in fluid processing and a method of fluidseparation, including a method of internal heat recovery therein.

BACKGROUND OF THE INVENTION

[0002] Membrane-assisted fluid separation processes are used to separatefluid mixtures into permeate and retentate portions. These processes maybe effected within fluid separation modules that contain a plurality ofhollow fiber membranes arranged in an elongated bundle encased in asingle shell containment housing. The conventional fluid separationmodules using hollow fiber membranes may be configured in either a shellside feed design or a bore side feed design.

[0003] Typically, fluid separation modules containing a plurality ofhollow fiber membranes arranged in a bundle have potting material, forexample epoxy, or other suitable material covering a portion of theexternal surface of each membrane within a bundle, for purposes ofsecuring the membranes within a module. If the resin is not properlyapplied and leakage of feed occurs from any of the membranes, suchleakage results in the contamination of permeate extracted from thehollow interior of the membrane. Similarly, if leakage-occurs for anyother reason, contamination of the fluid permeate results. Accordingly,one of the disadvantages of having a single module containing hundredsto thousands of membranes is that a defect in just one membrane rendersthe entire module, with all of the remaining intact membranes, useless.

[0004] In order to avoid this limitation, prior art devices use a largenumber of modules interconnected with one another in serial or parallelfashion, in order to increase the number of hollow membranes used andthus to increase the total membrane surface area across which a givenfluid mixture can be separated into its constituent permeate andretentate portions. If leakage occurs in any module, it can be replacedwhile minimizing the number of usable membranes discarded in theprocess.

[0005] These prior art devices still present two major problems. First,if there is a defect in a given membrane within a module that houses alarge number of hollow fiber membranes, the entire module containing thedefective membrane must be replaced, resulting in the wastage of allother usable membranes in the defective module. Moreover, in manyconventional membrane modules, the housing is made of expensive materialor the physical size of said housing is so large that it renders thedisposal of the housing for each module along with the membranescontained therein very uneconomical. Second, whether conventionalmodules are arranged in series or parallel fashion, extensive plumbingis necessary in order to connect the various modules and to remove thepermeate and retentate from each module. This extensive plumbing addssignificantly to the cost of manufacturing and maintaining these priorart devices. The plumbing also significantly adds to the complexity andbulkiness of these devices.

[0006] In general, thermally driven fluid separation processes withinconventional membrane-assisted fluid separation modules, especiallythose processes in which there is a large fraction of liquid feedseparated as permeate by evaporation through membranes, are very energyintensive and consuming.

[0007]FIG. 1 outlines the typical flow scheme for prior art vacuummembrane distillation operating within a conventional membrane-assistedfluid separation module. In a typical prior art membrane-assisted fluidseparation module 2, permeate vapours exiting the separation module arefirst condensed in a condenser 4 by using a cooling fluid source such ascooling water. The condensed liquid and non-condensable portions of thepermeate are then separated in a gas-liquid separation vessel 6. Avacuum pump 8 is attached to the gas-liquid separation vessel to pumpout non-condensable portions of the permeate and to sustain a vacuum onthe permeate side.

[0008] Extensive heat is required to preheat the feed to the temperaturerequired for optimum operation and to provide heat for vaporization forthe permeate. Also cooling means (for example, cooling water, chilledwater) have to be provided to remove the heat from the permeatecondenser. The operation of the process according to prior art is thusvery energy intensive and wasteful, as the heat supplied is mainly lostin cooling means (e.g. cooling water etc.).

SUMMARY OF THE INVENTION

[0009] The present invention overcomes the above-mentioned problems ofthe prior art devices. Each bundle of hollow fiber membranes can beassembled prior to its insertion into the housing, no further processingof the bundles is required after being inserted into the housing, theoverall fluid separation module design is easy to disassemble and eachbundle within the housing can be replaced easily in straightforwardmanner. These are all desirable features for on-site service of membranedevices. Further, in the present invention, the need for extensiveplumbing apparatus to remove the permeate from the module is minimized,which reduces the cost, complexity and maintenance requirements of theinvention.

[0010] In a preferred embodiment of the invention, all of the bundles ofhollow fiber membranes have a common feed chamber, common permeatechamber and common retentate chamber instead of being housed in separatemodules interconnected by extensive plumbing. The feed fluid is thusintroduced into the bundles of membranes in a parallel fashion, and thecumulative permeate is extracted from the separation housing in bulk.Consequently, there is significantly less plumbing apparatus required tointroduce the feed fluid and to remove the permeate and retentate fromthe single fluid separation module. With this reduction of necessaryplumbing, the costs of the present invention are substantially less thanprior art devices and the present invention is easier to manufacture.

[0011] The present invention comprises a fluid separation module used toseparate a fluid mixture into permeate and retentate portions. While twoimportant applications for the present invention are desalination ofseawater by means of membrane distillation and removal of VOCs fromwater by means of vacuum membrane distillation or pervaporation, theapparatus can be used for a number of different fluid separationprocesses including, but not limited to, pervaporation, vapourpermeation, membrane distillation (both vacuum membrane distillation anddirect contact membrane distillation), ultra filtration,microfiltration, nanofiltration, reverse osmosis, membrane stripping andgas separation.

[0012] In the preferred embodiment of the invention, the fluidseparation module comprises a hollow housing that contains a pluralityof elongate hollow fiber membranes arranged in one or more bundles.Unlike conventional prior art devices, each bundle is not encased in itsown housing. The bundle or bundles of hollow fiber membranes areoriented in an axial direction within the housing.

[0013] Depending on the fluid separation process being used, the housingmay operate at a range of pressures from elevated pressures to vacuumconditions. In a first embodiment, the hollow housing has a first openend and an axially opposite second open end which are covered by a firstseal member and a second seal member, respectively. The first sealmember at the first open end of the housing contains openings throughwhich the ends of the hollow fiber membranes within each bundle areexposed and communicate with the feed side of the seal member, coveredby a first endcap. An open region is thus created between the interiorof the first endcap and the first seal member. Similarly, the secondseal member at the second open end of the housing contains openingsthrough which the second end of the hollow fiber membranes within theeach bundle are exposed and communicate with the other side of the sealmember, covered by a second endcap. An open region is thus createdbetween the interior of the second endcap and the second seal member.

[0014] In an alternative embodiment of this invention, the housing hasone open end. This opening is covered and sealed by a sealing membersuch as a removable endplate. At least one feed inlet passes through theremovable endplate and communicates with the bundle or bundles ofmembranes contained in the housing. At least one retentate outlet passesthrough the removable endplate and communicates with the interior of thehousing. Although, plumbing is required to interconnect the ends ofbundles of membranes, significantly less plumbing is required to extractpermeate from the common housing of this invention as opposed to theplumbing required to extract permeate from the interconnected modulesfound in the prior art.

[0015] In the shell side feed configuration of the present invention,the housing contains at least one feed inlet through which feed isintroduced to the interior of the housing. Once inside the housing, thefeed is introduced to the outside of the bundles of hollow fibermembranes and the permeate migrates through the membrane walls into thelumen of the hollow fiber membranes. The permeate exits through the endof the hollow fiber membranes, usually at the end that is longitudinallydistant from the fluid inlet. The pressure outside the membranes ismaintained higher than the pressure within the lumen of the membranes.The housing also contains at least one retentate outlet through whichretentate exits the housing.

[0016] In the bore side feed configuration of the present invention, thefeed is introduced into the lumen of the hollow fiber membranes at oneend and the permeate migrates through the membrane wall to the outsideof the membrane. The retentate remains in the lumen and exits the otherend of the hollow membranes. The pressure on the outside of themembranes is maintained lower than the pressure within the lumen of themembranes.

[0017] Although the shell side feed configuration differs from the boreside configuration as to where the feed enters the hollow fibermembranes and where the permeate and retentate are removed from thehousing, the structure of the housing, the principles for operating thefluid separation module, and principles of heat recovery all remain thesame in both configurations.

[0018] The present invention also provides a method of fluid separationwhich comprises a method for internal heat recovery, feasible forapplications where membrane-assisted fluid separation involves a largeportion of the feed evaporating through the membranes into permeate.Desalination of salt water and purification of contaminated water bymeans of vacuum membrane distillation are just two examples ofsituations where the internal heat recovery process may be applied. Inthese two examples, large portions of the feed is separated by membranesinto a high purity water permeate stream by evaporation through themembranes and into a retentate stream containing a higher concentrationof dissolved components than present in the feed.

[0019] In the internal heat recovery method taught by the presentinvention, permeate water vapour that is extracted from the fluidseparation module is compressed by an external compressor to increasethe temperature of the water vapour. This increased heat is thentransferred back to the incoming feed fluid mixture entering the fluidseparation module by means of a condenser/heat exchanger. By extractingheat from the permeate, the internal heat recovery process recycles mostof the heat used during the separation process. A minimal amount ofenergy is required to operate the compressor to compress the permeatevapours. The energy required for compression is low as compared to thetotal heat transferred within the internal heat recovery process. Assuch, the method of the invention utilizes energy efficiently inrelation to prior art apparatus.

[0020] The present invention thus provides a fluid separation apparatuscomprising: a hollow housing defining a separation chamber, having atleast one permeate outlet to permit one or more permeate components ofthe feed fluid mixture to exit the housing; at least one feed inlet forfeeding a fluid mixture into the housing; at least one bundle of hollowfiber membranes contained within the housing having first and secondopen ends, the first ends being in fluid communication with a feedinlet; and at least one retentate outlet to permit one or morenon-permeate components of the feed fluid mixture to exit the fluidseparation module, whereby the feed fluid mixture passes through thehollow fiber membranes such that the one or more permeate components ofthe feed fluid mixture migrate across the walls of the membranes to apermeate region defined between the fiber membranes and an interior wallof the housing, and the one or more retentate portions of the feed fluidmixture pass along the length of the membranes to the retentate outlet.

[0021] In further aspects of the apparatus of the invention: a housingwherein the ends of a bundle of hollow fiber membranes are each securedby a holding member comprising of a tube sheet, such that the ends ofthe hollow fiber membranes are exposed to the feed inlet and retentateoutlet, respectively; the bundle of hollow fiber membranes is supportedalong its length by at least two telescoping rods, each rod comprisingtwo or more rod portions interlocking in sliding relation; each rodconsists of at least three rod portions, comprising two end rods eachhaving one end fixed into the medial surface of a holding member and amedial rod, whereby opposite ends of the medial rod engage the two endrods in a telescoping relation; the two open ends of the housing aresealed by first and second sealing members respectively, each sealingmember comprising openings through which the ends of the bundle ofmembranes is inserted, whereby the ends of the hollow fiber membranesare exposed to a region external to each sealing member; each end of thebundle of membranes is secured by a holding member having a threadedportion, and the bundle is secured to each sealing member by threadedmembers engaging the threaded portions of the holding members; thebundle of hollow fiber membranes is encased in a sleeve that hasopenings, to protect the physical integrity of the hollow fibermembranes contained within said sleeve but allowing the passage offluids through the sleeve; a first endcap is secured to an inlet end ofthe housing such that a feed inlet region is defined between the firstendcap and the first sealing member; a second endcap is secured to anoutlet end of the housing such that a retentate outlet region is definedbetween the second endcap and the second sealing member; the firstendcap comprises a feed inlet; retentate exits the fiber membranesthrough the retentate outlet region; the second endcap comprises aretentate outlet; permeate traverses the walls of the hollow fibermembranes by means of pervaporation, vapour permeation, membranedistillation including vacuum membrane distillation, direct contactmembrane distillation, ultra filtration, microfiltration,nanofiltration, reverse osmosis, membrane stripping, gas separation or acombination thereof; a first heating area is defined between the firstendcap and the first sealing member and a second heating area is definedbetween the second endcap and the second sealing member, the first andsecond heating areas each providing at least one heating fluid inlet andat least one heating fluid outlet to allow the passage of heated fluidtherethrough; the feed inlet passes through the first endcap andsupplies feed fluid mixture directly to the end of at the bundle ofhollow fiber membranes in fluid-tight relation; the ends of the bundlesof hollow fiber membranes are interconnected in fluid-tightcommunication by conduits to create a series of serially connectedbundles of hollow fiber membranes through which the feed fluid mixtureis conveyed to the retentate outlet; the conduits are disposed withinthe first and second heating areas; the feed fluid mixture is heatedwithin the conduits by heated fluid passing over said conduits withinthe first and second heating areas; the feed fluid mixture is separatedinto permeate and retentate portions by means of pervaporation, vapourpermeation, membrane distillation including vacuum membranedistillation, direct contact membrane distillation, ultra filtration,microfiltration nanofiltration, reverse osmosis, membrane stripping, gasseparation or a combination thereof; the feed inlet passes through thefirst endcap and supplies feed fluid mixture directly to the end of atthe bundle of hollow fiber membranes in fluid-tight relation; the endsof the bundles of hollow fiber membranes are interconnected influid-tight communication by conduits to create a series of seriallyconnected bundles of hollow fiber membranes through which the feed fluidmixture is conveyed to the retentate outlet; the conduits are disposedwithin in the first and second heating areas; the feed fluid mixture isheated within the conduits by heated fluid passing over said conduitswithin the first and second heating areas; the feed fluid mixture isseparated into permeate and retentate portions by means ofpervaporation, vapour permeation, membrane distillation including vacuummembrane distillation, direct contact membrane distillation, ultrafiltration, microfiltration nanofiltration, reverse osmosis, membranestripping, gas separation or a combination thereof.

[0022] The present invention also provides a fluid separation apparatuscomprising: a hollow housing defining a separation chamber, having atleast one feed inlet to permit a fluid mixture to enter into the housingand at least one permeate outlet to permit the permeate to exit thehousing; at least one bundle of hollow fiber membranes contained withinthe housing having first and second open ends, the first ends being influid communication with the permeate outlet; and at least one retentateoutlet to permit one or more non-permeate components of the feed fluidmixture to exit the separation chamber; whereby the feed fluid mixturepasses through the separation chamber such that the one or more permeatecomponents of the feed fluid mixture migrate across the walls of themembranes into the lumen of the hollow fiber membranes and exit thehousing through the permeate outlet, and one or more of the retentateportions remaining in the housing exits the housing through theretentate outlet.

[0023] The present invention further provides a method for fluidseparation using membrane distillation, wherein a feed fluid isseparated into permeate and retentate components, comprising the stepsof: compressing permeate exiting a permeate outlet of a separationchamber, to create a compressed permeate; transferring heat ofcompression from the compressed permeate to the feed fluid in acondenser; and maintaining an operating pressure of the condenser bymeans of a vacuum pump in fluid communication with said condenser.

[0024] The present invention further provides a method for separatingfresh water from saltwater utilizing the module of claim 39, comprisingthe steps of: heating a saltwater feed entering the fluid membraneseparation module; separating a permeate of water vapour from thesaltwater under vacuum or vacuum-like conditions; passing the watervapour through a blower to compress the water vapour and therebyincrease temperature; passing the heated water vapour through a heatexchanger to heat the saltwater feed and condense the water vapour; andcollecting the condensed water.

[0025] In further aspects, the method of the invention is used for theremoval and recovery of fresh water from seawater by means of membranedistillation; or for the removal of volatile organic compounds fromwater by means of membrane distillation or pervaporation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In drawings which illustrate by way of example only preferredembodiments of the invention.

[0027]FIG. 1 is a schematic drawing of the flow of fluid during vacuummembrane distillation according to the prior art.

[0028]FIG. 2 is a perspective view of a preferred fluid separationmodule of the invention containing a plurality of bundles of hollowfiber membranes.

[0029]FIG. 3 is an exploded perspective view of a single bundle ofhollow fiber membranes in the module of FIG. 2.

[0030]FIG. 4 is a front elevational view of an end of the bundle ofhollow fiber membranes of FIG. 3.

[0031]FIG. 5 is a cross-sectional elevation of one preferred embodimentof the fluid separation module.

[0032]FIG. 6 is a cross-sectional view of an alternative embodiment ofthe fluid separation module.

[0033]FIG. 7 is perspective view of a further alternative embodiment ofthe fluid separation module.

[0034]FIG. 8 is a schematic elevation of an alternative embodiment ofthe fluid separation module with serially connected bundles.

[0035]FIG. 9 is a schematic elevation of a further alternativeembodiment of the fluid separation module with serially connectedbundles.

[0036]FIG. 10 is a schematic drawing of the flow of fluid in a systemincorporating the fluid separation module for use in the removal ofvolatile organic compounds from water.

[0037]FIG. 11 is a schematic drawing of the flow of fluid in a systemincorporating the fluid separation module in association with theinternal heat recovery process for use in the desalination of seawater.

[0038]FIG. 12 is a perspective view of an embodiment of the singlebundle of hollow fiber membranes having a telescopic protective casing.

[0039]FIG. 13 is an exploded perspective view the bundle of hollow fibermembranes illustrated in FIG. 12.

[0040]FIG. 14 is a perspective view of an embodiment of the singlebundle of hollow fiber membranes having a one-piece protective casing.

[0041]FIG. 15 is an exploded view of the bundle of hollow fibermembranes illustrated in FIG. 14.

[0042]FIG. 16 is a perspective view of an alternative embodiment of thefluid separation module.

[0043]FIG. 17 is an exploded view of a bundle of fiber in the module ofFIG. 16.

[0044]FIG. 18 is a perspective view of a group of bundles of fibers inthe module of FIG. 16.

[0045]FIG. 19 is a partial perspective view interconnected bundles offibers in the alternative module of FIG. 16.

[0046]FIG. 20A is a schematic elevation of the fluid separation moduleof FIG. 16 with a combination of series and parallel-connected bundles.

[0047]FIG. 20B is a schematic elevation of the fluid separation moduleof FIG. 16 with a combination of serially-connected bundles.

[0048]FIG. 21 is a schematic elevation of a further embodiment of thefluid separation module.

DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention provides a fluid separation module used toseparate fluid mixtures into permeate and retentate portions by means ofmembranes adapted for fluid separation. The fluid separation module maybe used to perform any membrane-assisted fluid separation processesincluding but not limited to, pervaporation, vapour permeation, membranedistillation (both vacuum membrane distillation and direct contactmembrane distillation), ultra filtration, microfiltration,nanofiltration, reverse osmosis, membrane stripping and gas separationor a combination of any of these processes.

[0050]FIG. 2 illustrates a first preferred embodiment of the fluidseparation apparatus 10 of the invention. The apparatus 10 comprises ahollow housing 12 that contains within the lumen of the housing 12, aplurality of elongate hollow fiber membranes 14 which are grouped in atleast one bundle 16. Preferably, the housing 12 will contain a pluralityof bundles of hollow fiber membranes 16. The bundles 16 are orientedaxially within the housing 12. The housing 12 is preferably made ofstainless steel, plastic or any other suitable material which is capableof protecting the fluid separation module from the environment, capableof withstanding the operating temperatures and pressures under which theseparation process is effected and will not corrode or decompose tocontaminate the fluids contained within the module.

[0051] The housing 12 has a first end 18 and a second end 20. A permeateoutlet 44 is located along the body of the housing 12 allowing the lumenof the housing 12 to communicate with the pumping system external to thehousing 12, to extract the permeate from the housing 12. For certainfluid separation processes, such as pervaporation, vapour permeation andmembrane distillation, the separation of the fluid mixture within thelumen of the housing 12 will operate under vacuum or vacuum-likeconditions as described below.

[0052] The hollow fiber membranes 14 are all approximately the samelength and preferably range in length from about 5 cm to about 2000 cm,preferably about 10 cm to about 200 cm and most preferably between about50 to about 150 cm. The diameter of the hollow fiber membranes willpreferably range from about 0.1 mm to about 50 mm.

[0053] Each hollow fiber membrane 14 has a first end and a second end.FIGS. 2 and 4 show one end 22 of a bundle 16 of hollow fiber membranes14. The ends 22 of the bundle 16 of hollow fiber membranes 14 areembedded in a tube sheet 46 formed by potting material, for exampleepoxy or other suitable material. Moreover, each bundle 16 of hollowfiber membranes 14 is held together at both the first and second ends bya holding member, for example, a bundle end connector 24, as shown inFIG. 3, which also serves to secure the bundle 16 within the housing 12.The ends 22 of each hollow fiber membrane 14 within a given bundle 16are inserted through the lumen of a bundle end connector 24 such thatthe ends 22 of the hollow fiber membranes 14 are approximately flushwith the outer end of the bundle end connector 24. The ends 22 of thehollow fiber membranes 14 are secured in place within the lumen of thebundle end connector 24 by potting material, for example, epoxy or othersuitable material 46, best seen in FIG. 3, forming a tube sheet whichsurrounds the ends 22 of the hollow fiber membranes 14 but does notimpinge into the lumen of the hollow fiber membranes 14. The ends 22 ofthe bundle 16 of hollow fiber membranes 14 are thus exposed through thetube sheet 46 such that the ends may communicate with the region on theother side of the tube sheet 46 opposite the fiber bundle 16. The tubesheet 46 at the bundle end connector 24 is created by processes wellknown in the art.

[0054] As shown in FIG. 3, each bundle 16 of hollow fiber membranes 14is preferably supported by two or more telescoping rods 48. Eachtelescoping rod 48 consists of two or more rod portions, with adjacentportions interlocking in sliding relation to allow the rods 48 to beshortened or lengthened as required. FIG. 3 illustrates the preferredembodiment, which includes three telescoping rods 48. Preferably, eachtelescoping rod 48 consists of three rod portions, including two endrods 48 a each having one end fixed into the medial surface of bundleend connector 24. The two end rods 48 a are connected by a medial rod 48b such that the opposite ends of the medial rod 48 b engage the two endrods 48 a in telescoping relation.

[0055] As shown in FIG. 3, the telescoping rods 48 provide structuralsupport to each bundle 16 of hollow fiber membranes 14. Thus, whileprior art devices encase each bundle of hollow fiber membranes in asingle housing, according to the present invention no individual casingis required to surround a single bundle of hollow fiber membranes 14 andthe telescoping rods 48 provide the necessary structural support. Thetelescoping rods 48 also provide adjustability of the bundle 16 in theaxial direction. This adjustability is useful because, while the ends 22of the fibers 14 should be precisely aligned at the ends of the bundle16, it is difficult to cut the fibers 14 with the precision necessary toensure that each is exactly the length corresponding to the distancebetween bundle support plates 30. Thus, once the bundle end connectors24 are adhered to the fibers 14, the telescoping rods 48 allow thebundle 16 to be compressed axially in order to precisely fit within thelength of the housing 12 during module assembly without detracting fromthe structural integrity of the bundle 16. The telescoping rods 48 alsoprovide flexibility to expand axially when the threaded bundle retainer34 are tightened as said retainer 34 pulls the bundle end connecters 24which in turn pulls the fiber bundles 16 outwardly. Individual hollowfiber membranes 14 within a bundle 16 that may be slightly longer thanother membranes 14 within the same bundle 16 will splay outwardlyslightly to accommodate the adjustment, with no material effect on theoperation of the invention.

[0056] As shown in FIG. 2, the housing 12 has two open ends 18 and 20both of which are sealed by means of a gasket 28 and a sealing member,for example, a bundle support plate 30. A similar gasket 28 and bundlesupport plate 30 seals the open end 20 of the housing 12. The bundlesupport plate 30 provides bundle end openings 32 for each bundle 16contained within the lumen of the housing 12. Surrounding the narrowerportion of the bundle end connector 24 is a bundle sealing ring 26. Aflange portion of the bundle end connector 24 has a diameter larger thanthe narrower portion of said connector. The narrower portion of thebundle end connector 24 is inserted into the bundle opening 32 and thebundle sealing ring 26 abuts the face of the bundle support plate 30facing the interior of the housing 12. The entire open end 18 of thehousing 12 is sealed by securing the gasket 28, and in turn the bundlesupport plate 30, to the flange 19 that extends outwardly from the openend 18 of the housing 12. At least part of narrower portion of eachbundle end connector 24 is threaded, upon which threaded bundleretainers, for example nuts 34, are engaged to secure the bundles 16.The narrower portion of the bundle end connectors 24 thus protrudethrough the bundle end opening 32 of the bundle support plates 30, andthe bundle sealing ring 26 forms a seal between the bundle endconnectors 24 and the inner face of the bundle support plate 30 byfastening the threaded bundle retainers 34 to secure the bundles 16. Theinterior of the housing 12 is thus sealed with the ends 22 of the fiberhollow fiber membranes 14 exposed beyond the bundle support plate 30 andcontained within the open regions between the bundle support plates 30and the endcaps 40.

[0057] The housing 12 further comprises endcaps 40 located at either endof the housing 12. FIG. 2 illustrates the inlet endcap 40 which, alongwith gasket 36, bundle support plate 30 and gasket 28, engages and issecured to the flange 19 of the housing 12 by means of bolts or anyother suitable fastening means. Once secured to the housing 12, the openregion defined between the bundle support plate 30 and the inlet endcap40 defines the feed inlet region 54 manifold, best seen in FIG. 5. Theinlet endcap 40 contains a feed inlet 42 which permits access into thefeed inlet region 54. The structure and attachment of the outlet endcap41 at the second open end 20 of the housing 12 is the same as describedabove as illustrated in cross-sectional view in FIG. 4, with the openregion created by the outlet endcap 41 and the second bundle supportplate 43 defining a retentate outlet region 56, and the outlet endcap 41provides a retentate outlet 48 which connects the retentate outletregion 56 with the environment external to the module 10.

[0058] Once the housing 12 is sealed, the regions beyond the bundles 16of hollow fiber membranes 14 within the main chamber of the housing 12defines a permeate outlet region 50 (see FIG. 5). Permeate whichmigrates through the bundle or bundles 16 of hollow fiber membranes 14from within the lumen of the membranes 14 collects in the permeateoutlet region 50 before exiting the module 10 through the permeateoutlet 44.

[0059] As illustrated in FIGS. 6 and 7, alternate configurations of thefluid separation module 10 consist of plurality of bundle support plates30 sharing one common housing 12. Each of the bundle support plate 30supports a single or a plurality of bundles 16. The common housing mayhave a common feed chamber, common permeate chamber and common retentatechamber. Alternatively, each support plate 30 may have attached to itits own feed chamber and retentate chamber, but the housing 12containing a common permeate chamber. This feature provides theadvantage of permitting access to each individual bundle plate 30 forservicing, for initial installation of bundles 16, and for allowingdifferent fluid mixture to be fed through each individual feed chamber.

[0060] For a system requiring large membrane area, the total number ofbundles 16 can be significant. These alternate arrangements help to keepthe total number of hollow fiber bundles 16 attached to an individualbundle support plate to within reasonable limits. The housing 12 mayhave a plurality of feed inlets, retentate outlets and permeate outlets.Where the single housing 12 contains a plurality of bundle supportplates 30 then support for the non-circumferential edges of thesesupport plates 30 will be provided by additional support and fasteningmeans.

[0061] In one alternative embodiment, the bundle of membranes 16 areencased in a sleeve 200 that is knitted, perforated, porous or otherwisehas openings 202 as shown in FIG. 12. The purpose of the sleeve 200 isto protect the physical integrity of the hollow fiber membranes 14contained within the sleeve 200 but still allow the passage of fluidsthrough the sleeve 200 such that there maybe fluid communication betweenthe hollow fiber membranes 14 and the interior of the housing 12. Thesleeve 200 is made of plastic, metal or other suitable material thatwill not corrode or decompose contaminating the fluids contained withinthe module. To maintain the adjustability of the bundle 16 of membranes,the sleeve 200 may consist of two or more elements as shown in FIGS. 12and 13 as 200 a and 200 b, that move telescopically in relation to oneanother. The telescopic rods 48 may or may not be present in thisalternative embodiment.

[0062] In another embodiment of bundle design as illustrated in FIG. 14,one end of a bundle of membranes 16 is secured to the bundle endconnector 24 and the opposite end of the bundle 16 is secured to thebundle support plate 30 in a fluid tight slip-fit engagement within anopening 203 in the bundle support plate 30. The fluid tight slip-fitengagement is effected by a slip-fit bundle end connector 204 and asealant, for example an O-ring 206. The slip-fit bundle end connector204 contains and holds together an end of the bundle 16 of hollow fibermembranes 14 by means of a tube sheet as described previously. An O-ring206 surrounds a narrow portion of a slip-fit bundle end connector 204.The narrow portion of the slip-fit bundle end connector 204 and O-ring206 are inserted into the lumen of an opening 203 in the bundle supportplate 30. In this embodiment, force may be applied to the opposite axialend of the bundle 16 to push the combination O-ring 206 and slip-fitbundle end connector 204 into the opening 203 in the bundle supportplate 30. The O-ring 206 acts to secure the narrow end of the slip-fitbundle end connector 204 in a fluid-tight seal within the opening 203 ofthe bundle support plate 30. If there is more than one bundle 16 ofhollow fiber membranes connected to a bundle support plate 30, then thecombination of slip-fit bundle end connector 20 and O-ring 206 islocated at the end of the bundle 16 to be inserted into the bundlesupport plate 30. The bundle support plate 30 has the appropriate numberof openings 203 in it to receive the slip-fit bundle end connector 20and O-ring 206 assembly from each bundle 16. The advantage of thisbundle arrangement is the ease in which bundles 16 of fiber membranescan be inserted into and removed from the housing 12. The ends of thebundles 16 containing the slip-fit bundle end connector 204 and O-ring206 combination are merely physically pushed in or pulled out of thebundle support plate 30. Physical force is applied at the axiallyopposite end of the bundle 16 from the slip-fit end containing thebundle end connector 204 and O-ring 204 combination to install thebundles 16 and the support plate 30 is then installed to the housing 12.Given that physical force can be applied to install the bundle 16 ofhollow fiber membranes, structural support means is helpful for thebundle 16 to counter such force. Such support means may be provided byusing a rigid, not telescopic, sleeve 200 that at least in partsurrounds the bundle 16 of hollow fiber membranes. The presence ofsupporting rods 48 are an additional but optional form of support means,but said rods, if present, would be preferably rigid and not telescopic.

[0063] In yet another alternative bundle design, the ends of differentbundles 16 of fiber membranes are interconnected in fluid-tightcommunication by conduits to create a series of serially connectedbundles 16 of hollow fiber membranes through which the feed fluidmixture is conveyed. This arrangement is illustrated in FIG. 17. Theends of the fiber membranes 14 are contained within a conduit bundle endconnector 220. A conduit bundle end connector 220 also uses a tube sheet48 to contain and hold the ends of the hollow fiber membranes 14 withina bundle 16 as previously described. Within the lumen of the conduitbundle end connector 220, the ends of the hollow fiber membranes 14 aresecured in place by a tube sheet 46 formed by potting material, forexample, epoxy or other suitable material, which is conventional andknown to someone skilled in the relevant art. The conduit bundle endconnector 220 does not pass through the bundle support plate 30.Instead, a bundle end connector cap 222 is connected to the conduitbundle end connectors 220 on either end of the bundle 16 of hollow fibermembranes 14. This connection may for example be effected by a threadedconnection between the bundle end connector cap 222 and the conduitbundle end connector 220. The bundle end connector cap 222 is hollowsuch that fluid passing in or out of the ends of the hollow fibermembranes 14, may pass through the bundle connector cap 222. A fluidconduit 224 attaches to the bundle end connector cap 224 at a secondopening in said cap 222. The fluid conduit 224 is comprised of one ormore components. The other end of said fluid conduit 224 connects to thebundle end connector cap 222 and conduit bundle end connector 220assembly of a different bundle 16 of hollow fiber membranes. Thisarrangement permits two or more bundles 16 to be connected to oneanother, permitting fluid to pass through each bundle 16 of hollow fibermembranes in fluid-tight communication. In this embodiment, some or allof the bundles 16 of hollow fiber membranes may be surrounded by thesleeve 200.

[0064]FIG. 18 illustrates several bundles 16 of hollow fiber membranesconnected to one another in a series arrangement. This configurationpermits fluid to pass through a connected bundles 16 of hollow fibermembranes.

[0065] The various configurations of bundle design described above havethe advantage of flexibility and ease of assembly.

[0066] Operation of the Fluid Separation Module

[0067] The fluid separation module 10 may thus be used to separate fluidmixtures into permeate and retentate portions by means of membranes 14arranged in bundles 16 adapted for fluid separation. The flow of thefluid mixture and resulting permeate and retentate through the fluidseparation module will be first be described in detail with reference toFIGS. 2 and 5.

[0068] A feed fluid mixture enters the fluid separation module 10through the feed inlet 42 and enters the feed inlet region 54 definedbetween the inlet endcap 40 and the bundle support plate 30. Within thefeed inlet region 54, the ends 22 of the bundles 16 of hollow fibermembranes 14 embedded in tube sheets 46 are exposed to the feed fluidmixture. The feed fluid mixture enters the lumen of the individualhollow fiber membranes 14 contained within the membrane bundle orbundles 16. As the feed fluid mixture passes along the length of thehollow fiber membranes 14, the desired permeate traverses across themembrane walls and either passes directly into the permeate outletregion 50 beyond the bundles 16 of membranes 14, or first flows throughthe interstitial spaces between the membranes 14 within and betweenbundles 16 and then eventually flows to the permeate outlet region 50.The permeate collected within the permeate outlet region 50 exits themodule 10 through permeate outlet 44.

[0069] As the feed fluid mixture moves along the length of the hollowfiber membranes 14, permeate continues to be extracted and thenon-permeate (retentate) component or components of the feed fluidmixture becomes more concentrated. The retentate leaves the lumen of thehollow membrane fibers 14 at the second end of the membranes 14. Asshown in FIG. 5, the second end of the hollow fiber membranes 14communicate with the retentate outlet region 56 defined between thesecond bundle support plate 43 and the second endcap 41. The retentateexits the ends of the hollow fiber membranes 14 and enters the retentatefluid outlet region 56, from which the retentate leaves the module 10through the retentate outlet 48.

[0070]FIG. 8 illustrates an alternative embodiment of the apparatus ofthe invention, in which the fiber bundles 16 are connected in serialfashion. In this embodiment, the feed inlet region 54 does not serve asa manifold; rather, the feed fluid mixture enters the feed inlet 42 andis channelled directly into the hollow fiber membrane ends 22 of one ormore selected bundle 16 of membranes 14 (one bundle 16 in the embodimentshown). The other bundles 16 have the ends 22 of their respectivemembranes 16 facing the feed inlet region 54 but connected to oneanother by means of sealed caps 74 overlaying the ends 22 and tubing 78connecting the caps 74 in fluid-tight communication. The retentateexiting the outlet ends 22 of the initially selected bundle or bundles16 of membranes 14 is thus connected by means of tubing 78 through caps76 to the end of an adjacent bundle 16. The advantage of thisarrangement is that the feed fluid mixture moves along the length ofseveral hollow fiber membranes 14, increasing the separation time andallowing greater amounts of permeate to be extracted as the feed becomesmore concentrated. The concentration of permeating portion in theretentate portion of the feed fluid mixture is much less in this serialarrangement of the bundles 16 than could be obtained by a parallelbundle configuration of similar bundle length and diameters asillustrated in FIG. 6. Another advantage to this arrangement is thatbundles 16 of different types of membranes may be used in order toextract an array or plurality of permeate components from the feed fluidmixture.

[0071] A potential drawback experienced with the embodiment of FIG. 8 isthat as the feed fluid mixture moves further along the series ofinterconnected bundles 16, the temperature of the feed may decreasedepending on the separation process being used. In particular, where thepassage of permeate through the membrane is accompanied by a phasechange from liquid to vapour state (e.g. as occurs in pervaporation andvacuum membrane distillation) the temperature of the fluid mixture fromwhich the permeate is separated decreases as a result of the expenditureof the latent heat of vaporization required for the phase change. Thisis more likely when the bundles 16 are arrange in series which resultsin higher amounts of permeate removal from the feed mixture. Thereduction in fluid mixture temperature may cause a significant decreasein the efficiency of the fluid separation process as one of the forcesdriving the flow of permeate through the membranes is the partialpressure difference between the permeating portion in the feed fluidmixture and the side of the membrane exposed to the vacuum, namely thepermeate outlet region 50. Although the partial pressure of thepermeating component in the permeate outlet region 50 substantiallyremains the similar across the module 10, the partial pressure candecrease significantly with the decrease in temperature of the fluidfeed mixture on the feed side of the membrane.

[0072]FIG. 9 thus illustrates a further alternative embodiment of thefluid separation module 10 of the invention with serially connectedbundles 16. In this embodiment, the interconnecting tubing 78 betweenthe ends of the bundles 16 is located in the heating regions 80 and 82which are defined by the areas on both sides of the housing 12, namelybetween the first endcap 40 and the first bundle support plate 30; andbetween the second endcap 41 and the second bundle support plate 43;which are isolated from the feed fluid by sealed caps 74, 76. Eachheating area contains a heating fluid inlet 84 and a heating fluidoutlet 86. A heating fluid is injected through the heating areas throughthe heating fluid inlet 84, passes over and heats the retentate flowingthrough the interconnecting tubes 78 and the feed inlet 42 and exits theheating areas 80 and 82 through the respective heating fluid outlets 86.To increase the efficiency of the heat transfer, the interconnectingtubes 78 may be made of material with high thermal conductivity, may bein the form of coil to provide more heat transfer area and/or may havefins on the outside surface to provide additional heat transfer surface.The source of the heating fluid may be from an external source or from asource recycled within the system. The heating fluid may be steam,heated glycol/water mixture, commercial heat transfer fluids or othersimilar fluid. The connecting tubes 78 in the illustrated embodiment arecoiled, to increase the surface exposed area to the heating fluid andthus increase the rate of heat transfer.

[0073]FIG. 16 illustrates an embodiment of the invention, in which thefiber bundles 16 as illustrated in FIG. 17 are connected in serialfashion. However, in this embodiment, the bundles 16 of hollow fibermembranes are contained within a housing 12 that has an opening at onlyone end of the housing 12. The bundles 16 of hollow fiber membranes maybe supported within the housing 12 by a support structure 228 of varyingsuitable designs and can be mechanically attached to the bundle supportplate 30. At least one bundle 16 of hollow fiber membranes is attachedto the bundle support plate 30 by a fluid inlet 230 through which fluidmay pass from the exterior of the bundle support plate 30 and housingitself and eventually into the lumen of the hollow fiber membraneswithin the attached bundle 16. As a result, the fluid may pass throughthe lumen of the hollow fiber membranes within the bundles 16 that areserially connected to one another. The advantage of serially connectingthe fiber bundles 16 is increased separation time for the fluid withinthe lumen of the hollow fiber membranes of the connected bundles 16 ascompared to the separation time for fluid treated within bundlesarranged in a parallel manner. After the fluid has passed through thebundles 16, the retentate exits the housing 12 through a retentateoutlet 232. The retentate outlet 232 is attached at one end to at leastone bundle 16 of hollow fiber membranes and said outlet passes throughthe bundle support plate 30. One advantage of this alternativeconfiguration is the increased ease in which the entire group of bundlesmay be inserted into and removed from the housing 12. There is no needto remove both ends of the bundles 16 from bundle support plates 30 atboth ends of the bundle. The group of bundles 16 attached to the singlebundle support 30 act may act as a single unit. Another advantage isthat the group of bundles 16 may be easily tested as a single unit forleaks prior to insertion and use in the housing. Instead of testingindividual bundles 16 of hollow fiber membranes for leakage, the entiregroup of bundles 16 may be submerged in fluid outside of the housing andtested for leaks. For any leaks that are detected, the source of theleak can be identified and the specific bundle can be replaced. Then,the entire unit of bundles 16 may be easily inserted into the housing12. Finally, this configuration, removes the need for endcaps 40 on oneor both ends of the housing 12. The bundle support plate 30, may act asthe external seal to the housing 12. A gasket or similar structure isplaced between the bundle support plate 30 and the external seal. FIG.19 provides a detailed view of the group of the bundles 16 of hollowfiber membranes contained within the housing 12.

[0074]FIGS. 20A, 20B and 21 provide further alternative configurationsfor the housing 12. These alternative configurations illustrate that thevariety of arrangement the bundles 16 may assume within the housing 12to maximize the space within the housing 12 and that the structure ofthe housing 12 may assume different configurations. In each of theseconfigurations, like the embodiment in FIG. 16, the housing 12 containsonly one open end through which the bundles 16 of hollow fiber membranesare to be inserted.

[0075]FIG. 20A illustrates the group of bundles 16 of hollow fibermembranes connected to one another at their respective ends in acombination series and parallel arrangement. FIG. 20B illustrates thegroup of bundles 16 connected to one another at their respective ends ina series arrangement.

[0076] In the alternative embodiment shown in FIG. 21, the side of thehousing 12 covered by the bundle support plate 30, is further covered byan endcap 240 such that there is a space between the interior of theendcap 240 and the bundle support plate 30. This space is divided intotwo separate compartments, 240 a and 240 b. Compartment 240 a isconnected to a feed inlet 242 through which feed passes through andcommunicates with the open ends of the bundle 16 hollow fiber membranesexposed through the bundle support plate 30. Similarly, compartment 240b receives the retentate that passes through the bundles 16 of hollowfiber membranes and the retentate exits the housing through theretentate outlet 244.

[0077] Fluid Separation Processes

[0078] The fluid separation process or combination of processes beingpracticed within the fluid separation module 10 will determine thenature of the membrane or membranes 14 being used. The fluid separationprocesses that may be effected within the fluid separation moduleincludes but is not limited to, pervaporation, vapour permeation,membrane distillation (both vacuum membrane distillation and directcontact membrane distillation), ultra filtration, micro filtration,nanofiltration, reverse osmosis, membrane stripping and gas separation.Each of these processes is well known in the art. The hollow fibermembranes 14 may either be porous or non-porous. Generally, porousmembranes are used in membrane distillation and membrane stripping andnon-porous membranes are used in reverse osmosis and pervaporationapplications. Moreover, depending on the fluid sought to be separated,the membranes 14 may be either hydrophobic, hydrophilic ororganophillic.

[0079] When using the fluid separation module 10 in pervaporation andvacuum membrane distillation, a vacuum is applied outside the hollowfiber membranes 14. The permeable components from the feed fluid mixturepermeate across the membranes and are extracted from the module 10 asvapour which can then be condensed to liquid.

[0080] In direct contact membrane distillation, hydrophobic micropourousmembranes separate streams of fluids of differing temperature. For suchprocesses the fluid separation module 10 is modified slightly to containa separate fluid inlet (not shown) to allow the cooler fluid streamenter the module 10, run along the outside of the hollow fiber membranes14 and eventually exit the module 10 via an outlet (not shown). Thetemperature gradient across the membranes causes water vapour to passthrough the pores of the membranes and to condense on the other side ofthe membrane in the colder stream of fluid.

[0081] In ultrafiltration, microfiltration, nanofiltration and reverseosmosis, the feed fluid mixture in the module 10 is pressurized andportions of the feed permeate through the membrane and are removed asliquid.

[0082] In membrane stripping, membrane pores strip out a gas from agas-liquid mixture and the permeate is removed as a gas.

[0083] The fluid separation module may be used for a host of otherpossible applications, including but not limited to:

[0084] separation of organic liquid mixtures (pervaporation, vapourpermeation);

[0085] production of pure water suitable for pharmaceutical and foodindustries (vacuum membrane distillation or reverse osmosis);

[0086] concentrate juices and fragrance compounds in the food andperfume industries, respectively (pervaporation or vacuum membranedistillation);

[0087] removal of water from bio-reactors (pervaporation or vacuummembrane distillation);

[0088] recycling of process solution by extracting diluents (vacuummembrane distillation);

[0089] treatment of contaminated fluids (vacuum membrane distillation,reverse osmosis, ultrafiltration);

[0090] separation of ultrafine particles and bacteria from water(ultrafiltration)

[0091] The fluid separation module of the invention is particularly wellsuited for the removal of VOCs from water by means of either membranedistillation or pervaporation. Where the membrane distillation processis used for this application, the membranes 14 will be porous andhydrophobic. For pervaporation processes, the membranes 14 will benon-porous and hydrophobic or organophilic.

[0092] Another particularly useful application for this invention isdesalination by means of membrane distillation of seawater in whichfresh water is removed from the fluid mixture as permeate. In thisapplication, the membranes are porous and hydrophobic in composition.This prevents water in the liquid phase, with dissolved brine and othersolids, from seeping through the membranes 14, while permitting purewater vapour to migrate through the membranes 14.

[0093] The application of the fluid separation module 10 to the removalof VOCs from water and to desalination of seawater will be discussedbelow in detail. However, these two applications are merely examples ofthe possible applications that this invention may perform and are notlimiting.

[0094] Removal of Volatile Organic Compounds from (“VOCs”) Water

[0095] As illustrated in FIG. 10, the incoming feed (VOCs and watermixture) is supplied from a given source. The feed moves to heatexchanger 114 at which point the feed is heated further to a range fromabout 10° C. to about 80° C. by means of heat transfer from heatedretentate (treated water) leaving the fluid separation module 10. Thefeed may pass a secondary heater 116, if required, at which point thefeed reaches its optimum temperature range of about 15° C. to 98° C. andpreferably in the vicinity of the boiling of water at the pressure atwhich the permeate outlet side of the module 10 is operated.

[0096] The feed enters the fluid separation module 10 in which permeateoutlet region 50 is operating under vacuum or vacuum-like conditionswith the preferred permeate side and sub-ambient pressures ranging fromabout 0.05 psia to about 14.6 psia and preferably between about 0.1 psiato about 12 psia. As the feed passes along the axial lengths of thelumen of the hollow fiber membranes 14, the feed continually losespermeate by evaporation through the membrane pores. Heat loss due to theevaporation of permeate may result in the temperature of the feed todrop significantly below the optimum operating temperature, especiallywhen the bundles 16 of hollow fiber membranes 14 are arranged in series.In such circumstances where there is a significant drop in temperature,the feed is heated continuously by built-in inter-stage heaters 118.

[0097] The incoming feed enters the ends 22 of at least one bundle 16 ofhollow fiber membranes 14 and travels along the axial length of thelumen of said bundle 16 and in turn passes along the axial lengths ofthe lumen of the other bundles 16 of hollow fiber membranes 16 withinthe fluid separation module 10.

[0098] As the feed moves along the length of the series of bundles 16 ofhollow fiber membranes 14, the permeate consisting of VOC and traceamounts of water are extracted from feed. The permeate enters thepermeate outlet region 50 of the fluid separation module 10 and exitsthrough the permeate outlet 44. The escaping permeate is in vapourphase.

[0099] The permeate vapour leaving the separation module 10 through theoutlet 44 are condensed and sub-cooled in a condenser 90 into liquidmixture of VOCs and water. The liquid permeate is then stored in asettling tank 122 where the VOCs are separated by means well known inthe art from the water (e.g. separation by gravity). The VOCs arecollected. The water rich phase is circulated back into the incomingfeed. The non-condensable portions of the permeate, mainly dissolvedgases and some traces of VOCs vapours in the feed, are constantlyremoved by a vacuum pump 120 attached to the gas settling tank andmaintains the vacuum on the permeate site of the system. Vacuum pumpeffluents before venting may be first passed through a bed of activatedcarbon or similar adsorbent to remove traces of any entrained VOCsvapours (not shown).

[0100] A wide variety of types vacuum pumps which are known by oneskilled in the art may be used including, but not limited, to rotaryvane, rotary lobe type, or screw type. However, dry vacuum pumps (rotarylobe, screw type or others) capable of achieving the required with theinternals that protect the contact of pumping medium with the pumpinternal lubricating oil, and which are specially designed for handlingharsh fluids that the pump may be exposed to are preferred.

[0101] The retentate (in this process treated water) exits the end 22 ofthe one or more bundles 16 of hollow fiber membranes 14 and exits themodule 10 through the retentate outlet 48. The temperature range for theretentate leaving said module 10 is between about 10° C. to about 95° C.The exiting retentate transfers heat to the incoming feed at pre-heater114. Then the treated water is collected.

[0102] Internal Heat Recovery Method

[0103] The present invention provides a novel method of internal heatrecovery 130 where the permeate heat of vaporization is transferred backto the incoming feed by employing a blower/compressor 132 to compressthe permeate vapours exiting the membrane-assisted fluid separationmodule 10 as illustrated in FIG. 11. In contrast to the prior art shownin FIG. 1, permeate vapours exiting the module are first condensed in acondenser 134 using a cooling fluid source. The novel method in thepresent invention may be applied in membrane-assisted fluid separationapplications which have significant evaporation of permeate through themembranes 14.

[0104] In the present invention, the compressor outlet temperaturevaries significantly according to the ratio of compressor outlet andcompressor inlet pressures (called compression ratio). The higher thecompression ratio, the higher will be compressor outlet temperature. Acompression ratio anywhere between 1.02 to 50.0 and preferably 1.2 to 10can be used to increase the compressor outlet temperatures by anywherefrom few degrees Celsius to several hundred degrees Celsius, althoughother compression ratios may be appropriate in some processes.

[0105] The terms “blower” and “compressor” are terms used hereininterchangeably for devices with low compression ratios. Actualselection of a blower/compressor will vary from application toapplication and will be apparent to one skilled in the art. Centrifugalor rotary positive displacement type blowers/compressors may be used.The centrifugal compressors/blowers are preferred as they provide lesspulsation in the system, offer higher energy efficiency, and aresuitable for handling large volumetric flow rates that may be necessaryfor large industrial scale operation. These compressors should haveadequate sealing mechanism to operate under vacuum and should notcontaminate the permeate vapours by their internal lubricating oil.

[0106] One possible way of controlling the compressor outlet pressure isby adjusting the condenser operating pressure. This is achieved by usinga means of creating a vacuum in the condenser 134, such as a secondaryvacuum pump 136 illustrated in FIG. 11. This secondary vacuum pump 136constantly removes the non-condensable portions of the permeate from thecondenser 134 and maintains the desired pressure in it.

[0107] By adjusting the optimum compression ratio the temperature ofpermeate vapour exiting the compressor 132 can be adjusted to a valueslightly higher than the module feed inlet temperature. These vapourswhen condensed in the condenser 134 at temperatures higher than the feedtemperature result in the transfer of latent heat from vaporization tothe incoming liquid feed on the other side of the condenser 134 andbrings the feed temperature to the desired module inlet conditions.

[0108] Application of this internal heat recovery method makes thevacuum membrane distillation highly energy efficient and makes it afeasible process even for application where separation takes place byevaporating a significant fraction of feed into permeate through themembrane.

[0109] Desalination and contaminated water purification are examples ofapplications that may utilize the of method internal heat recovery astaught by this invention. In these applications, large portions of feedare separated by a membrane into a high purity water permeate stream byevaporation through the membranes and a retentate stream with higherconcentration of non-permeating components such as dissolved salts,other soluble impurities and non-volatile compounds. The method ofinternal heat recovery is not limited to these two examples, but thismethod may be applied to any membrane-assisted fluid separationapplication which has significant evaporation of permeate through saidmembranes.

[0110] Desalination

[0111] Both the module and the method of internal heat recoverydisclosed by the present invention can be used in association with oneanother in certain applications where membrane-assisted fluid separationtakes place by evaporating a significant fraction of the feed intopermeate through the membrane. Desalination of seawater by means ofvacuum membrane distillation is one example. Removal of lowconcentrations VOCs from water differs because a significant fraction ofthe feed is not evaporated into permeate.

[0112]FIG. 11 outlines the flow pattern scheme for desalinationutilizing this novel method of heat recovery. The incoming feed (e.g.saltwater) is supplied from a particular source (e.g. the sea) and isinitially split into two streams 138 a and 138 b respectively. One feedsplit stream is heated by heated retentate that has left the fluidseparation module 10 at heat exchanger 140. The other feed split streamis heated by means of heat transfer from the heated permeate at heatexchanger 142. Feed side effluents of the two exchangers 140 and 142 arethen combined into one feed stream such that the combined feedtemperature ranges from about 40° C. to about 85° C. At the condenser134, the feed is heated further to a preferred temperature range between50° C. and 100° C. by the permeate before the feed fluid enters thefluid separation module 10 at a pressure of about 15 psia to about 40psia.

[0113] Permeate outlet region of the fluid separation module 10 isoperating under vacuum or vacuum-like conditions with the preferredpermeate side and sub-ambient pressures ranging from about 0.05 psia toabout 14.6 psia and preferably between about 0.1 psia to about 12 psiaAs the feed passes along the axial lengths of the lumen of the hollowfiber membranes 14, the feed continually looses permeate by evaporationthrough the membrane pores.

[0114] Depending on the temperature of feed and the vacuum level in theretentate outlet side of the separation module 10, the temperature ofpermeate vapour exiting the module 10 can range from about 30° C. to 90°C. These permeate vapours are heated by the compressor 132 to increaseits temperature to provide sufficient driving force for heat transfer totake place between the heated permeate vapours and colder feed enteringthe condenser 134. Compressed vapour temperature can range from about50° C. to 200° C.

[0115] The retentate exits the fluid separation module 10 at atemperature lower than the incoming feed fluid mixture but still greaterthan the temperature of the feed fluid mixture coming from the feedsource. At the heat exchanger 140 the heated retentate (concentrate) isused to heat one incoming feed split stream. A portion of the outgoingheated retentate can be recycled back with the incoming feed to extractmore pure water from it if required.

[0116] Of the different fluid separation processes that may be used inthe fluid separation module 10, pervaporation, vapour permeation andmembrane distillation all preferably heat the incoming feed fluidmixture and may require inter-stage heaters for series operation.

[0117] The operating temperatures and pressures provided above,particularly for the examples of removal of VOCs from water anddesalination are given as a reference only and can deviate significantlywithin and outside of the ranges specified. These parameter rangeslargely depend on, but are not limited to, factors such as thecomposition and properties of the fluid mixtures to be separated, typesof membranes used, and composition of the permeate and retentate.

[0118] Preferred embodiments of the invention having been thus describedby way of example, it will be apparent to those skilled in the art thatcertain modifications and adaptations may be made without departing fromthe scope of the invention, as set out in the appended claims.

What is claimed is:
 1. A fluid separation apparatus comprising: a. a hollow housing defining a separation chamber, having at least one permeate outlet to permit one or more permeate components of the feed fluid mixture to exit the housing; b. at least one feed inlet for feeding a fluid mixture into the housing; c. at least one bundle of hollow fiber membranes contained within the housing having first and second open ends, the first ends being in fluid communication with a feed inlet; and d. at least one retentate outlet to permit one or more non-permeate components of the feed fluid mixture to exit the fluid separation module; whereby the feed fluid mixture passes through the hollow fiber membranes such that the one or more permeate components of the feed fluid mixture migrate across the walls of the membranes to a permeate region defined between the fiber membranes and an interior wall of the housing, and the one or more retentate portions of the feed fluid mixture pass along the length of the membranes to the retentate outlet.
 2. The apparatus of claim 1 wherein the ends of a bundle of hollow fiber membranes are each secured by a holding member comprising a tube sheet, such that the ends of the hollow fiber membranes are exposed to the feed inlet and retentate outlet, respectively.
 3. The apparatus of claim 1 wherein the housing has two open ends which are sealed by first and second sealing members respectively, each sealing member comprising openings through which the ends of the bundle of membranes is inserted, whereby the ends of the hollow fiber membranes are exposed to a region external to each sealing member.
 4. The apparatus of claim 3 wherein each end of the bundle of membranes is secured by a holding member having a threaded portion, and the bundle is secured to each sealing member by threaded members engaging the threaded portions of the holding members.
 5. The apparatus of claim 3 wherein one end of the bundle of membranes is secured to a holding member by threaded members engaging threaded portions of the holding member, and the opposite end of the bundle of membranes is secured to the sealing member in a fluid-tight slip fit engagement.
 6. The apparatus of claim 1 wherein the housing has one open end sealed by means of a sealing member containing at least one opening through which a feed inlet passes whereby the feed inlet connects to the ends of at least one bundle of membranes by means of a connecting member, and said sealing member contains at least one opening through which a retentate outlet passes, whereby the retentate outlet connects to the ends of at least one bundle of membranes.
 7. The apparatus of claim 2 wherein the bundle of hollow fiber membranes is supported along its length by one or more rods.
 8. The apparatus of claim 7 wherein the rod bundle of hollow fiber membranes is supported along its length by at least two telescoping rods, each rod comprising two or more rod portions interlocking in sliding relation.
 9. The apparatus of claim 8 wherein each rod consists of at least three rod portions, comprising two end rods each having one end fixed into the medial surface of a holding member and a medial rod, whereby opposite ends of the medial rod engage the two end rods in a telescoping relation.
 10. The apparatus of claims 2 wherein the bundle of hollow fiber membranes is enclosed in a sleeve that has openings, the sleeve protecting the physical integrity of the hollow fiber membranes contained within said sleeve but allowing the passage of fluids through the sleeve.
 11. The apparatus of claim 10 wherein the sleeve consists of two or more elements that move telescopically in relation to one another.
 12. The apparatus of claim 6, wherein the two or more bundles of membranes are connected to one another in series.
 13. The apparatus of claim 6, wherein the two or more bundles of membranes are connected to one another in parallel.
 14. The apparatus of claim 6 wherein two or more bundles of membranes are physically supported by a bearing means against the interior of the housing.
 15. The apparatus of claim 2 wherein a first endcap is secured to an inlet end of the housing such that a feed inlet region is defined between the first endcap and the first sealing member.
 16. The apparatus of claim 15 wherein a second endcap is secured to an outlet end of the housing such that a retentate outlet region is defined between the second endcap and the second sealing member.
 17. The apparatus of claim 16 wherein the first endcap comprises a feed inlet.
 18. The apparatus of claim 17 wherein retentate exits the fiber membranes into the retentate outlet region.
 19. The apparatus of claim 18 wherein the second endcap comprises a retentate outlet.
 20. The apparatus of claim 6 wherein one or more endcaps is secured to the end of the housing such that a feed inlet region is defined between said endcap and the sealing member, and a retentate outlet region is defined between said endcap and the sealing member, and the feed inlet region and retentate outlet region are physically separate from one another.
 21. The apparatus of claim 20, wherein the endcap creating the feed inlet region has at least one opening through which a feed inlet passes and empties feed into said feed inlet region.
 22. The apparatus of claim 21, wherein the endcap creating the retentate outlet region has at least one opening through which a retentate outlet passes and permits retentate within the retentate outlet region to exit the housing.
 23. The apparatus of claim 1 wherein permeate traverses the walls of the hollow fiber membranes by means of pervaporation, vapour permeation, membrane distillation including vacuum membrane distillation, direct contact membrane distillation, ultra filtration, microfiltration nanofiltration, reverse osmosis, membrane stripping, gas separation or a combination thereof.
 24. The apparatus of claim 16 wherein a first heating area is defined between the first endcap and the first sealing member and a second heating area is defined between the second endcap and the second sealing member, the first and second heating areas each providing at least one heating fluid inlet and at least one heating fluid outlet to allow the passage of heated fluid therethrough.
 25. The apparatus of claim 15 wherein the feed inlet passes through the first endcap and supplies feed fluid mixture directly to the end of at the bundle of hollow fiber membranes in fluid-tight relation.
 26. The apparatus of claim 25 wherein the ends of the bundles of hollow fiber membranes are interconnected in fluid-tight communication by conduits to create a series of serially connected bundles of hollow fiber membranes through which the feed fluid mixture is conveyed to the retentate outlet.
 27. The apparatus of claim 26 wherein the conduits are disposed within in the first and second heating areas.
 28. The apparatus of claim 27 wherein the feed fluid mixture is heated within the conduits by heated fluid passing over said conduits within the first and second heating areas.
 29. The apparatus of claim 28 wherein the feed fluid mixture is separated into permeate and retentate portions by means of pervaporation, vapour permeation, membrane distillation including vacuum membrane distillation, direct contact membrane distillation, ultra filtration, microfiltration nanofiltration, reverse osmosis, membrane stripping, gas separation or a combination thereof.
 30. The apparatus of claim 26 wherein the feed inlet passes through the first endcap and supplies feed fluid mixture directly to the end of at the bundle of hollow fiber membranes in fluid-tight relation.
 31. The apparatus of claim 30 wherein the ends of the bundles of hollow fiber membranes are interconnected in fluid-tight communication by conduits to create a series of serially connected bundles of hollow fiber membranes through which the feed fluid mixture is conveyed to the retentate outlet.
 32. The apparatus of claim 31 wherein the conduits are disposed within in the first and second heating areas.
 33. The apparatus of claim 32 wherein the feed fluid mixture is heated within the conduits by heated fluid passing over said conduits within the first and second heating areas.
 34. The apparatus of claim 26 wherein the feed fluid mixture is separated into permeate and retentate portions by means of pervaporation, vapour permeation, membrane distillation including vacuum membrane distillation, direct contact membrane distillation, ultra filtration, microfiltration nanofiltration, reverse osmosis, membrane stripping, gas separation or a combination thereof.
 35. The apparatus of claim 1 for use in the process of desalination.
 36. The apparatus of claim 35 wherein the housing operates under a vacuum in or vacuum-like conditions with the preferred permeate side and sub-ambient pressures ranging from about 0.05 psia to about 14.4 psia.
 37. The apparatus of claim 36 wherein the housing operates under a vacuum in or vacuum-like conditions with the preferred permeate side and sub-ambient pressures ranging preferably from about 0.1 psia to about 12.0 psia.
 38. The apparatus of claim 1 wherein the hollow fiber membranes are porous.
 39. The apparatus of claim 1 wherein the hollow fiber membranes are hydrophobic.
 40. A fluid separation apparatus comprising: a. a hollow housing defining a separation chamber, having a feed inlet to permit a fluid mixture to enter into the housing and a permeate outlet to permit the permeate to exit the housing; b. at least one bundle of hollow fiber membranes contained within the housing having first and second open ends, the first ends being in fluid communication with the permeate outlet; and c. at least one retentate outlet to permit one or more non-permeate components of the feed fluid mixture to exit the separation chamber; whereby the feed fluid mixture passes through the separation chamber such that the one or more permeate components of the feed fluid mixture migrate across the walls of the membranes into the lumen of the hollow fiber membranes and exit the housing through the permeate outlet, and one or more of the retentate portions remaining in the housing exits the housing through the retentate outlet.
 41. The apparatus of claim 40 wherein the feed fluid mixture is separated into permeate and retentate portions by means of pervaporation, vapour permeation, membrane distillation including vacuum membrane distillation, direct contact membrane distillation, ultra filtration, microfiltration nanofiltration, reverse osmosis, membrane stripping, gas separation or a combination thereof.
 42. The apparatus of claim 41 for use in the process of desalination. 43 A method for fluid separation, wherein a feed fluid is separated into permeate and retentate components, comprising the steps of: a. compressing permeate exiting a permeate outlet of a separation chamber, to create a compressed permeate; b. transferring heat from the compressed permeate to the feed fluid in a condenser; and c. maintaining an operating pressure of the condenser by means of a vacuum pump in fluid communication with said condenser.
 44. The method of claim 43 for the removal and recovery of fresh water from seawater by means of membrane distillation.
 45. The method of claim 44 wherein for the removal of volatile organic compounds from water by means of membrane distillation or pervaporation.
 46. A method for separating fresh water from saltwater utilizing the module of claim 39, comprising the steps of: d. heating a saltwater feed entering the fluid membrane separation module; e. separating a permeate of water vapour from the saltwater under vacuum or vacuum-like conditions; f. passing the water vapour through a condenser or blower to increase the pressure of the water vapour; g. passing the heated water vapour through a heat exchanger to heat the saltwater feed and condense the water vapour; and h. collecting the condensed water. 